Trichomycterus guaraquessaba, Wolmar B. Wosiacki, 2005

Wolmar B. Wosiacki, 2005, A new species of Trichomycterus (Siluriformes: Trichomycteridae) from south Brazil and redescription of T. iheringi (Eigenmann)., Zootaxa 1040, pp. 49-64 : 51-56

Trichomycterus guaraquessaba n. sp.

(Fig. 2, Table 1)

Holotype: MPEG 7916 (89.1mm SL); rio Bracinho, Fazenda Salto Dourado, Município de Guaraqueçaba, Paraná, Brazil; Wosiacki, W. B. and Mateus, J. C., 13 August 1994.

Paratypes: MPEG 7917, 2 exs. (85.3 91.5 mm SL, C&S) , MHNCI 7916, 3 ex. (68.0 82.0 mm SL) , MZUSP 85531, 2 exs. (82.8-86.0 mm SL), collected with holotype .

Diagnosis: No uniquely derived features were found to diagnose T. guaraquessaba . Trichomycterus guaraquessaba shares with T. castroi de Pinna , T. davisi (Haseman) , T. iheringi , T. mboycy Wosiacki & Garavello , T. naipi Wosiacki & Garavello , T. papilliferus Wosiacki & Garavello , T. plumbeus Wosiacki & Garavello , T. stawiarski (MirandaRibeiro) , and T. zonatus (Eigenmann) the first pectoral-fin ray not prolonged as a filament and differs from all other congeners from south and southeastern Brazil [ T. albinotatus Costa , T. alternatus (Eigenamnn) , T. auroguttatus Costa , T. bahianus Costa , T. brasiliensis Luetken , T. candidus (Miranda-Ribeiro) , T. caudofasciatus Alencar & Costa , T. concolor Costa, T. giganteus Lima & Costa , T. goeldii Boulenger , T. immaculatus (Eigenmann & Eigenmann) , T. itacambirussu Triques & Vono , T. itatiayae Ribeiro , T. jequitinhonhae Triques & Vono , T. landinga Triques & Vono , T. longibarbatus Costa , T. maracaya Bockma & Sazima , T. mimonha Costa , T. mirissumba Costa , T. nigricans Valenciennes , T. pantherinus Alencar & Costa , T. potschi Barbosa & Costa , T. taroba Wosiacki & Garavello , T. trefauti Wosiacki , T. reinhardti (Eigenmann) , T. triguttatus (Eigenmann) , T. variegatus Costa , and T. vermiculatus (Eigenmann) ] by the presence of the first pectoralfin ray prolonged as a filament. Trichomycterus guaraquessaba shares with the larger assemblage of species congeners from south and southeastern Brazil the presence of two pores s6 paired at the interorbital space [vs. one symphyseal pore s6 in T. alternatus , T. giganteus , T. nigricans , and T. paquequerensis (Miranda-Ribeiro) ]. Trichomycterus guaraquessaba shares with T. castroi , T. iheringi , T. plumbeus , and T. stawiarski I-7 pectoral-fin rays (vs. I-5 in T. mboycy , T. naipi , and I-6 in T. davisi , T. papilliferus , and T. zonatus ). Trichomycterus guaraquessaba is readily distinguished from T. castroi and T. stawiarski by the uniformly gray color pattern with small spots scattered over the flank and side of the caudal peduncle (vs. large and well defined spots and stripes). Furthermore, T. guaraquessaba can be distinguished from T. iheringi , T. plumbeus , and other congeners by the combination of the pelvic-fin margin not covering the urogenital opening (vs. covering the urogenital opening), and caudal-fin margin strongly truncate (vs. with attenuated edges, rounded or bilobed).

Description: Morphometric data for holotype and paratypes are given in Table 1.

Body elongate, roughly cylindrical close to head and gradually more compressed in trunk towards caudal fin. Profiles of trunk straight dorsally and slightly convex ventrally. Dorsal and ventral profiles of caudal peduncle straight (Fig. 2). Integument thick, especially over base of dorsal and anal fins. Small papillae on lips and scattered over lateral surface of head.

Head depressed, trapezoidal, or longer than wide (18.9-19.9 % SL), the transversal section at posterior tip of opercle wider than anteriorly at nostril, anterior margin straight (Fig. 4). Lateral region of eye slightly swollen by jaw muscles in both large and small specimens. Profiles of head straight dorsally and convex ventrally. Eyes rounded, well defined rim, dorsally oriented, covered by thin skin, not distinctly separated from surface of eyeball. Ocular structures readily visible on surface of skin, not deeply sunken. Orbital rim not free. Anterior nostril larger than posterior, surrounded by fleshy flap of integument. Posterior nostril surrounded anteriorly by thin flap of integument. Anterior nostril same size as eye diameter. Gill membranes thick, united to isthmus only at anteriormost point. Gill openings not constricted. Seven branchiostegal rays externally (8 in C&S) visible from below. Mouth subterminal, its corners laterally oriented. Lower lip with conspicuous lateral fleshy lobes, internal to origin of rictal barbels. Anterior margin of upper lip rounded. Small papillae on external surface of upper lip and large papillae continuous inside mouth at region of teeth attachment. Upper lip continuous with dorsal surface of head. Barbels long: nasal 58.1-81.9, maxillary 66.7-83.9, and rictal barbel length 53.3-71.0 % HL. Barbels with large bases and gradually narrowing towards tip. Nasal barbels reaching base of anterior opercular odontodes; maxillary barbels reaching tip of posterior opercular odontodes; rictal barbels reaching tip of posterior most interopercular odontodes. Origin of nasal barbels on posterolateral portion of integument flap around anterior nostril. Interopercular patch of odontodes long, 22-23 conical odontodes covered by thick integument; external series smaller and straight and internal series larger, curved medially. Opercular patch of odontodes rounded, with 18-19 conical odontodes, anterior ones smaller and straight, posterior ones larger and curved medially. Sensory canals composed of supraorbital canal complete and infraorbital incomplete. Infraorbital anterior section pores i1 and i3, and posterior section pores i10 and i11. Supraorbital pores s1, s2 and s6. Two pores s6 paired at interorbital space.

Pectoral fin with truncate margin, I-7 rays, first longest ray not prolonged as short filament. Dorsal fin with margin semicircular, II/6- 8 (Holotype, II-7) rays, second the longest. Anal fin slightly elongate in overall shape, slightly smaller than dorsal fin, II-5 rays, second the longest, origin at vertical through last dorsal-fin ray. Pelvic fin with origin anterior to dorsal-fin origin, rounded margin, not in contact with anal and urogenital openings, I-4 rays, third the longest. Caudal-fin margin strongly truncate, without attenuated edges, margin slightly wider than remaining caudal region, I/11/I principal rays, branched rays splitting three times. Only the first dorsal and ventral caudal-fin accessory rays visible. Anal and urogenital openings closer to anal-fin origin than to pelvic-fin base.

Free vertebrae 37. Ribs 14-15 pairs, first one thickest, second to 12-13th pairs slightly longest, last pair rudimentary and free. Dorsal-fin pterygiophores 8, first inserting in front of neural spine of 18th free vertebra. Anal-fin pterygiophores 6, first inserting in front of haemal spine of 22nd free vertebra. Dorsal procurrent rays 15. Ventral procurrent rays 8. Caudal skeleton composed of pleurostyle, hypurals fused 3+4+5, and fused parahypural and hypurals 1+2.

Color pattern: Refer to figure 4 for general view of color pattern in alcohol. The pattern is the same for smaller (68.9mm SL) to larger (89.1mm SL) specimens. Uniform gray on dorsal surface of trunk, gradually lighter laterally. Dorsal surface of head gray, darker on occipital region. Cheek, over the jaw-muscle lighter, with few chromatophores. Nasal barbel with few chromatophores on dorsal surface. Maxillary and rictal barbels slightly pigmented on dorsal surface. Ventral surfaces of head, trunk and caudal peduncle unpigmented. Small spots, less than half eye-diameter, scattered over flank and lateral of caudal peduncle and caudal fin. Pectoral fin with few chromatophores over dorsal surface from base to half of length-rays. Pelvic fins unpigmented. Anal fin with few chromatophores from base to half of ray length, lighter than dorsal fin. Dorsal fin with few chromatophores over rays, darker at base, gradually lighter to tip. Caudal fin with small uniform spots from base to tip, over rays and inter-rays, larger and darker at base, gradually small and light to tip.

Distribution: Known only from the type locality.

Etymology: The specific epithet “guaraquessaba” is derived from the name of Município de Guaraqueçaba and the Área de Proteção Ambiental de Guaraqueçaba (APA- Guaraqueçaba), the area of occurrence of the new species. A noun in apposition.

Remarks: Trichomycterus and Trichomycterinae are not monophyletic groups, but the allocation of T. guaraquessaba to this genus is the best solution for maintaining nomenclatural stability. Trichomycterus guaraquessaba does not have the features observed in Bullockia , Eremophilus , Hatcheria , Rhizosomichthys , Silvinichthys , all formerly included in Trichomycterinae, and can not be allocated to any of these genera. The morphological similarity among Trichomycterus species is high and the identification is, often, impossible without the examination of type material. Few species present distinct autapomorphies ( T. castroi , T. ramosus Fernandez , T. papilliferus , T. trefauti ), and most species have been diagnosed by the combination of characters. The last revision of the group was made by Eigenmann (1918) and included the transcriptions of the original descriptions of all species known for the time. It is the best reference for the identification of Trichomycteridae species, but its descriptions, keys and drawings are outdated. Trichomycterus guaraquessaba could be correctly recognized as a new species only after the examination of the type material of T. iheringi . Trichomycterus guaraquessaba is slightly similar to this species in color pattern, but it is distinguished by the number of dorsal branched rays (6-8 vs. 9-10), caudal-fin margin strongly truncate (vs. rounded), pectoral girdle width (13.5-14.7 vs. 15.2-17.0 % SL), body depth (12.6-14.4 vs. 14.9- 17.9 % SL), nasal barbel length (58.1-81.9 vs. 25.2-43.1 % HL), maxillary barbel length (66.7-83.9 vs. 37.2-47.2 % HL), and rictal barbel length (53.3-71.0 vs. 22.3-37.7 % HL). A strongly truncate caudal-fin margin is a feature shared by few species of Trichomycterinae, e.g., T. immaculatus , T. heterodontus (Eigenmann) and Ituglanis parkoi (Miranda-Ribeiro) . However, T. guaraquessaba is distinct among these species by the combination of other characteristics presented above. On the other hand, a truncate caudal fin with attenuated edges is shared by a large assemblage of species ( T. castroi , T. zonatus , T. paolence , T. reinhardti , T. davisi , T. alternatus , T. papilliferus and T. plumbeus , and T. trefauti ), all occurring in the south and southeastern Brazil plus T. taczanowskii Steindachner from Peru. The large majority of Trichomycterinae species have a rounded caudal-fin margin like that of Nematogenyidae [ Nematogenys inermis (Guichenot) ], the sister group of Trichomycteridae. A phylogenetic analysis is necessary to understand the role of the caudal-fin shape in elucidating the relationships of Trichomycterinae species.

Ecological notes: The rio Bracinho, type locality of Trichomycterus guaraquessaba , is a typical Atlantic Rain Forest stream, with clear water, falls, rapids and moderate current flowing over the rocky beds, intercalated with pools. The river runs in an alluvial valley bordered by the slopes of adjacent hills, and the riparian vegetation is a dense, well preserved forest. Trichomycterus guaraquessaba occurs associated with stones and plant debris on the bottom and is syntopic with Astyanax sp., Deuterodon langei Travassos , Hollandichthys multifasciatus (Eigenmann & Norris) , Mimagoniates microlepis (Steindachner) , Characidium sp., Oligosarcus hepsetus (Cuvier) , Rhamdioglanis sp., Pimelodella sp., Acentronichthys leptos Eigenmann & Eigenmann , Rhamdia quelen (Quoy & Gaimard) , Ancistrus sp., Pseudotothyris obtusa (Miranda-Ribeiro) , Scleromystax barbatus (Quoy & Gaimard) , and Gymnotus carapo Linnaeus .